<template>
	<view>
		<view id="_drag_button" class="drag"
			:style="{left:`${left}px`,top:`${top}px`,backgroundColor:`${backgroundColor}`}" @touchstart="touchstart"
			@touchmove.stop.prevent="touchmove" @touchend="touchend" @click.stop.prevent="click"
			:class="{transition: isDock && !isMove }">
			<slot />
		</view>
	</view>
</template>

<script>
	/*
	属性名				类型				默认值		说明
	isDock				Boolean			false		是否启用自动停靠
	existTabBar			Boolean			false		当前页面是否包含tabbar
	backgroundColor		Boolean						背景颜色
	@btnClick			EventHandle					点击时会触发
	@btnTouchstart		EventHandle					拖拽开始时会触发
	@btnTouchend		EventHandle					拖拽结束时会触发
	*/
	export default {
		name: 'drag-button',
		props: {
			isDock: {
				type: Boolean,
				default: false
			},
			existTabBar: {
				type: Boolean,
				default: false
			},
			backgroundColor: {
				type: String,
				default: ""
			},
		},
		data() {
			return {
				top: 0,
				left: 0,
				width: 0,
				height: 0,
				offsetWidth: 0,
				offsetHeight: 0,
				windowWidth: 0,
				windowHeight: 0,
				isMove: false,
				edge: 10,
				idleTime: false,
				timeoutID: null,
			}
		},
		mounted() {
			this.init()
		},
		methods: {
			init() {
				const sys = uni.getSystemInfoSync();

				this.windowWidth = sys.windowWidth;
				this.windowHeight = sys.windowHeight;

				// #ifdef APP-PLUS
				this.existTabBar && (this.windowHeight -= 50);
				// #endif
				if (sys.windowTop) {
					this.windowHeight += sys.windowTop;
				}

				const query = uni.createSelectorQuery().in(this);
				query.select('#_drag_button').boundingClientRect(data => {
					this.width = data.width;
					this.height = data.height;
					this.offsetWidth = data.width / 2;
					this.offsetHeight = data.height / 2;
					this.left = this.windowWidth - this.width - this.edge;
					this.top = (this.windowHeight - this.height) / 4 - this.edge;

					this.setIdleTime()
				}).exec();
			},
			click() {
				if (!this.idleTime) {
					this.$emit('btnClick');
				}
			},
			touchstart(e) { //触摸时
				this.$emit('btnTouchstart');
			},
			touchmove(e) { //移动时
				// 单指触摸
				if (e.touches.length !== 1) {
					return false;
				}

				this.isMove = true;

				this.left = e.touches[0].clientX - this.offsetWidth;

				let clientY = e.touches[0].clientY - this.offsetHeight;
				// #ifdef H5
				clientY += this.height;
				// #endif
				let edgeBottom = this.windowHeight - this.height - this.edge;

				// 上下触及边界
				if (clientY < this.edge) {
					this.top = this.edge;
				} else if (clientY > edgeBottom) {
					this.top = edgeBottom;
				} else {
					this.top = clientY
				}

			},
			touchend(e) { //触摸结束时
				if (this.idleTime) {
					this.left -= (this.offsetWidth + this.edge)
					setTimeout(() => {
						this.idleTime = false
					}, 50)
				}
				if (this.isDock) {
					let edgeRigth = this.windowWidth - this.width - this.edge;

					if (this.left < this.windowWidth / 2 - this.offsetWidth) {
						this.left = this.edge;
					} else {
						this.left = edgeRigth;
					}
				}

				this.isMove = false;

				this.setIdleTime()

				this.$emit('btnTouchend');
			},
			setIdleTime() {
				clearTimeout(this.timeoutID)
				this.timeoutID = setTimeout(() => {
					if (!this.isMove && !this.idleTime) {
						this.idleTime = true
						this.left += (this.offsetWidth + this.edge)
					}
				}, 5000)
			}
		}
	}
</script>

<style lang="scss">
	.drag {
		display: flex;
		justify-content: center;
		align-items: center;
		background-color: rgba(0, 0, 0, 0.5);
		box-shadow: 0 0 6upx rgba(0, 0, 0, 0.4);
		color: $uni-text-color-inverse;
		padding: 15upx;
		border-radius: 50%;
		font-size: $uni-font-size-sm;
		position: fixed;
		z-index: 999999;

		&.transition {
			transition: left .3s ease, top .3s ease;
		}
	}
</style>
